Field of the Invention
The present invention relates to a radiation imaging apparatus and a radiation imaging system.
Description of the Related Art
Radiation imaging apparatuses having matrix substrates with pixel arrays in which switches such as TFTs (thin film transistors) and conversion elements such as photoelectric conversion elements are combined have been put to practical use as radiation imaging apparatuses used for medical imaging diagnosis and non-destructive examination by means of radiation such as X-rays.
In recent years, consideration has been given to increasing the functions of radiation imaging apparatuses. One way of increasing the functions that has been considered is including a function of monitoring the irradiation of radiation. For example, this function enables detection of the timing at which irradiation of radiation from a radiation source starts, detection of the timing at which the irradiation of the radiation is to be stopped, and detection of the irradiation amount or the integrated irradiation amount of the radiation.
Japanese Patent Laid-Open No. 2012-15913 discloses a radiation detection apparatus that includes pixels for obtaining a radiation image and pixels for detecting radiation. With the radiation detecting apparatus disclosed in Japanese Patent Laid-Open No. 2012-15913, signals of pixels for obtaining a radiation image and signals of pixels for detecting radiation are read out from the same signal line via a switch.
Japanese Patent Laid-Open No. 2011-174908 also discloses a radiation detection apparatus that includes pixels for obtaining a radiation image and pixels for detecting radiation. With the radiation detection apparatus disclosed in Japanese Patent Laid-Open No. 2011-174908, a dedicated signal line for detecting radiation is provided, and photoelectric conversion elements of pixels for detecting radiation are directly connected to the dedicated signal line.
With the radiation detecting apparatus disclosed in Japanese Patent Laid-Open No. 2012-15913, signals of pixels for obtaining a radiation image and signals of pixels for detecting radiation are read out via the same signal line. Accordingly, the signal line has a large parasitic capacitance, and it is difficult to read out the signals at a high speed from the pixels for detecting the radiation. For this reason, it is difficult to accurately perform control of the end of exposure and the like.
With the radiation detection apparatus disclosed in Japanese Patent Laid-Open No. 2011-174908, the number of dedicated signal lines needs to be the same as the number of detection areas in order to individually detect the irradiation of radiation on any detection area. In particular, if multiple pixels for detecting radiation are arranged in one column, the same number of dedicated signal lines as the pixels need to be arranged in that column. This causes an increase in the array pitch of the pixels or a reduction in the sensitivity of the pixels.